1. Field of the Invention
The present invention relates to novel polyformal resins and a process for producing said resins, and more particularly to polyformal resins having excellent heat resistance and optical properties, and a process for efficiently producing said resins.
2. Description of Related Art
Various polyformal resins have heretofore been known. Japanese Patent Application Laid-Open No. 125297/1979, for example, discloses polyformal resins having various chemical structures. A typical example is a polyformal resin produced from 2,2-bis(4-hydroxyphenyl)propane (generally called "bisphenol A") and methylene chloride. This polyformal resin, however, has a disadvantage in that its heat resistance is not sufficiently high: the glass transition temperature is 85.degree. C. In connection with optical properties of the polyformal resin, its optical anisotropy is large, and the polyformal resin cannot be used as a material for production of optical instruments.